Props - Should I only use the correct one?

[ieuand]

To cut a long story short, I won a box of props on eBay, i only wanted one of the six, so I have 5 that were not the correct type for my 1963 Evinrude 18hp fastwin.

So I was toying with the idea of putting the others on eBay again, when I thought I'd see if any of them fitted my engine. So the original prop on mine is a "Evinrude/Johnson 304684 9-1/4" X11 - No Spines, Shear Pin type"

But after trying them out, two of the other props fit onto my drive shaft perfectly, so can I use these on my engine?

They are:
1) BBJV837 9 x 10 383629 No spines shear pin type
2) VPU 9 x 9 No spines shear pin type

So Looking through my Evinrude Shop manual, I can see that the Diameter and pitch and rake are different, but would that actually make any difference? (Especially if I'm only going to use them as emergency spares)

So I guess my questions are:
1) Can I use them?
2) Will they Damage the Shaft or other parts of the engine?

Thanks
Ieuan (newby)

 

[EricJRW]

Re: Props - Should I only use the correct one?

I think the spare idea is a good one, so I would definitely keep at least one. What I learned from doing my prop research is that when you lower the pitch your engine RPM can go up. So if you do throw a lower pitch prop on, just be careful that running at WOT does not cause you to exceed your engine's max RPM.

As to other affects, I'll leave that one to the seasoned experts.

 

[steelespike]

Re: Props - Should I only use the correct one?

I would get myself a Tinytach and a gps and test the props out.If the shaft size and pin size work they may be intended for your 18.If you haul a lot of weight the 10 or 9 might work better but check the rpm.Propped right and setup carefully the 18 should approach about 27 mph.on a 14-16 utility.